Non-linearity determination of positioning scanner of measurement tool

ABSTRACT

Determination of non-linearity of a positioning scanner of a measurement tool is disclosed. In one embodiment, a method may include providing a probe of a measurement tool coupled to a positioning scanner; scanning a surface of a first sample with the surface at a first angle relative to the probe to attain a first profile; scanning the surface of the first sample with the surface at a second angle relative to the probe that is different than the first angle to attain a second profile; repeating the scannings to attain a plurality of first profiles and a plurality of second profiles; and determining a non-linearity of the positioning scanner using the different scanning angles to cancel out measurements corresponding to imperfections due to the surface of the sample. The non-linearity may be used to calibrate the positioning scanner.

REFERENCE TO PRIOR APPLICATIONS

This application is a Divisonal application of co-pending U.S. patentapplication Ser. No. 12/013,787, filed on Jan. 14, 2008, which is herebyincorporated by reference.

BACKGROUND

1. Technical Field

The disclosure relates generally to measurement systems, and moreparticularly, to calibration of measurement systems.

2. Background Art

Calibration of measurement systems used in, for example, measuring ICchips during or after manufacturing, is essential to attain accuratemeasurements. Current practices of checking linearity and calibratingvertical displacement of a measurement tool use several step heightstandards. The same is true for horizontal displacement. That is, thetool is used to measure a number of structures having known heights orknown pitch standards for horizontal displacement. Limitations on theavailability of these standards and the uncertainty of the standardsmake this approach inadequate.

SUMMARY

Determination of non-linearity of a positioning scanner of a measurementtool is disclosed. In one embodiment, a method may include providing aprobe of a measurement tool coupled to a positioning scanner; scanning asurface of a first sample with the surface at a first angle relative tothe probe to attain a first profile; scanning the surface of the firstsample with the surface at a second angle relative to the probe that isdifferent than the first angle to attain a second profile; repeating thescannings to attain a plurality of first profiles and a plurality ofsecond profiles; and determining a non-linearity of the positioningscanner using the different scanning angles to cancel out measurementscorresponding to imperfections due to the surface of the sample. Thenon-linearity may be used to calibrate the positioning scanner.

A first aspect of the disclosure provides a method comprising: providinga probe of a measurement tool coupled to a positioning scanner; scanninga surface of a first sample with the surface at a first angle relativeto the probe to attain a first profile; scanning the surface of thefirst sample with the surface at a second angle relative to the probethat is different than the first angle to attain a second profile;repeating the scannings to attain a plurality of first profiles and aplurality of second profiles; and determining a non-linearity of thepositioning scanner using the different scanning angles to cancel outmeasurements corresponding to imperfections due to the surface of thesample.

A second aspect of the disclosure provides a system comprising: ameasurement tool including a probe coupled to a positioning scanner; afixture for holding a sample for scanning a surface of the sample withthe surface at a first angle relative to the probe to attain a pluralityof first profiles, and scanning the surface of the sample with thesurface at a second angle relative to the probe that is different thanthe first angle to attain a plurality of second profiles; and adeterminator for determining a non-linearity of the positioning scannerusing the different scanning angles to cancel out measurementscorresponding to imperfections due to the surface of the sample.

A third aspect of the disclosure provides a program product stored on acomputer-readable medium, which when executed, determines anon-linearity of a positioning scanner of a measurement tool, theprogram product comprising: program code for controlling scanning asurface of a sample with the surface at a first angle relative to aprobe coupled to the positioning scanner to attain a first profile;program code for controlling scanning the surface of the sample with thesurface at a second angle relative to the probe that is different thanthe first angle to attain a second profile; program code for controllingrepeating the scannings to attain a plurality of first profiles and aplurality of second profiles; and program code for determining anon-linearity of the positioning scanner using the different scanningangles to cancel out measurements corresponding to imperfections due tothe surface of the sample.

A fourth aspect of the disclosure includes a scanning probe microscopecomprising: a probe coupled to a positioning scanner; a fixture forholding a sample for scanning a surface of the sample with the surfaceat a first angle relative to the probe to attain a plurality of firstprofiles, and scanning the surface of the sample with the surface at asecond angle relative to the probe that is different than the firstangle to attain a plurality of second profiles; and a determinator fordetermining a non-linearity of the positioning scanner using thedifferent scanning angles to cancel out measurements corresponding toimperfections due to the surface of the sample.

A fifth aspect of the disclosure provides a computer-readable mediumthat includes computer program code to enable a computer infrastructureto determine a non-linearity of a positioning scanner of a measurementtool, the computer-readable medium comprising computer program code forperforming the method steps of the disclosure.

A sixth aspect of the disclosure provides a method of generating asystem for determining a non-linearity of a positioning scanner of ameasurement tool, the method comprising: obtaining a computerinfrastructure; and deploying means for performing each of the steps ofthe disclosure to the computer infrastructure.

The illustrative aspects of the present disclosure are designed to solvethe problems herein described and/or other problems not discussed.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of this disclosure will be more readilyunderstood from the following detailed description of the variousaspects of the disclosure taken in conjunction with the accompanyingdrawings that depict various embodiments of the disclosure, in which:

FIG. 1 shows a block diagram of an illustrative environment including anon-linearity determining system according to the disclosure.

FIG. 2 shows a flow diagram of embodiments of the non-linearitydetermining system of FIG. 1 according to the disclosure.

FIGS. 3A-3B show schematic diagrams of the non-linearity determiningaccording to the disclosure.

FIG. 4 shows a comparison of profiles illustrating the non-linearitydetermining according to the disclosure.

FIG. 5 shows residuals of profiles after linear regression.

FIG. 6 shows a difference between the profiles for determiningnon-linearity.

FIG. 7 shows an illustrative calibrated Z height measurement sample.

It is noted that the drawings of the disclosure are not to scale. Thedrawings are intended to depict only typical aspects of the disclosure,and therefore should not be considered as limiting the scope of thedisclosure. In the drawings, like numbering represents like elementsbetween the drawings.

DETAILED DESCRIPTION

Turning to the drawings, FIG. 1 shows an illustrative environment 100 ofa measurement tool according to the disclosure. To this extent,environment 100 includes a computer infrastructure 102 that can performthe various process steps described herein for determining anon-linearity of a positioning scanner 92 of a measurement tool 90. Inparticular, computer infrastructure 102 is shown including a computingdevice 104 that comprises a non-linearity determination system 106,which enables computing device 104 to determine and/or correct anon-linearity of a positioning scanner of a measurement tool byperforming the process steps of the disclosure.

Computing device 104 is shown including a memory 112, a processor (PU)114, an input/output (I/O) interface 116, and a bus 118. Further,computing device 104 is shown in communication with an external I/Odevice/resource 120 and a storage system 122. As is known in the art, ingeneral, processor 114 executes computer program code, such asnon-linearity determining system 106, that is stored in memory 112and/or storage system 122. While executing computer program code,processor 114 can read and/or write data, such as measurements, scanningprofiles, etc., to/from memory 112, storage system 122, and/or I/Ointerface 116. Bus 118 provides a communications link between each ofthe components in computing device 104. I/O device 118 can comprise anydevice that enables a user to interact with computing device 104 or anydevice that enables computing device 104 to communicate with one or moreother computing devices. Input/output devices (including but not limitedto keyboards, displays, pointing devices, etc.) can be coupled to thesystem either directly or through intervening I/O controllers.

In any event, computing device 104 can comprise any general purposecomputing article of manufacture capable of executing computer programcode installed by a user (e.g., a personal computer, server, handhelddevice, etc.). However, it is understood that computing device 104 andnon-linearity determining system 106 are only representative of variouspossible equivalent computing devices that may perform the variousprocess steps of the disclosure. To this extent, in other embodiments,computing device 104 can comprise any specific purpose computing articleof manufacture comprising hardware and/or computer program code forperforming specific functions, any computing article of manufacture thatcomprises a combination of specific purpose and general purposehardware/software, or the like. In each case, the program code andhardware can be created using standard programming and engineeringtechniques, respectively.

Similarly, computer infrastructure 102 is only illustrative of varioustypes of computer infrastructures for implementing the disclosure. Forexample, in one embodiment, computer infrastructure 102 comprises two ormore computing devices (e.g., a server cluster) that communicate overany type of wired and/or wireless communications link, such as anetwork, a shared memory, or the like, to perform the various processsteps of the disclosure. When the communications link comprises anetwork, the network can comprise any combination of one or more typesof networks (e.g., the Internet, a wide area network, a local areanetwork, a virtual private network, etc.). Network adapters may also becoupled to the system to enable the data processing system to becomecoupled to other data processing systems or remote printers or storagedevices through intervening private or public networks. Modems, cablemodem and Ethernet cards are just a few of the currently available typesof network adapters. Regardless, communications between the computingdevices may utilize any combination of various types of transmissiontechniques.

Measurement tool 90 may include any now known or later developed systemfor measuring that includes positioning scanner 92 and probe 94, e.g., ascanning probe microscope (SPM), atomic force microscope, profilometeror other form of mechanical probe system, including electron and opticalprobing systems. Probe 94 may be contacting or non-contacting.Measurement tool 90 may be a contact type tool or a non-contact typetool, or may have a selective contact mode and a non-contact mode. Asunderstood, probe 94 is scanned over a surface of sample 96 and measuresan interaction between the surface and the probe, resulting in anelectronic profile, i.e., an image including, for example, surfacetopography. Measurement tool 90 may include non-linearity determiningsystem 106 or it may be a separate system. In any event, measurementtool 90 can include a capacitance gauge 95, or some other gauge as afeedback control for positioning scanner 92. Capacitance gauge 95 isused to monitor the position of positioning scanner 92. Feedback fromcapacitance gauge 95 can be used to moderate the input voltage topositioning scanner 92 so the scanner will move in a controlled motionto precisely determine vertical position (height) versus lateralposition. That is, piezoelectric material is used to finely positionpositioning scanner 92 and thus probe 94 laterally (X-Y plane) andvertically (Z plane). This functioning may be incorporated in aclosed-loop feedback system, or the feedback system may be omitted.Positioning scanner 92 controls voltage to the actuator to extend probe94 towards sample 96 so that the probe tracks the surface. As one withskill in the art will recognize, measurement tool 90 may include avariety of other sub-systems and components not illustrated in FIG. 1.Measurement tool 90 is shown for use with one or more samples 96positioned on a fixture 98.

Fixture 98 may include any now known or later developed sample holdingmechanism capable of angling the sample(s) 96 about a horizontal axis(see FIG. 3), and consistently holding sample 96 such that reproducibleresults can be obtained. Fixture 98 may have predefined angles of tiltto hold sample 96 to achieve a desired vertical (Z) translation for agiven amount of lateral (X or Y) axis translation. More specifically,fixture 98 may include any now known or later developed structure toallow the necessary lateral, vertical and angling of sample 96, e.g.,motors, cams, electronic controls, etc. The method described here isalso applicable for determining the non-linearity of scanners in the X,Yplane. A sample for doing this would have its scan surface perpendicularto the X, Y plane and be positioned and scanned at two different anglesto cancel the scan surface roughness from the intrinsic non-linearity ofthe X or Y scanners.

As previously mentioned and discussed further below, non-linearitydetermining system 106 enables computing infrastructure 102 to, amongother things, determine a non-linearity of positioning scanner 92 ofmeasurement tool 90. To this extent, non-linearity determining system106 is shown including a scanner control 130, a fixture control 132, adeterminator 134 including an averager 136, a best line fitter 138, analigner 140, a differencer 142 and an evaluator 144. In addition, acalibrator 150 for calibrating positioning scanner 92 may also beprovided. Operation of each of these systems is discussed further below.However, it is understood that some of the various systems shown in FIG.1 can be implemented independently, combined, and/or stored in memoryfor one or more separate computing devices that are included in computerinfrastructure 102. Further, it is understood that some of the systemsand/or functionality may not be implemented, or additional systemsand/or functionality may be included as part of environment 100.

Referring to FIGS. 2-3 in conjunction with FIG. 1, embodiments of amethod of operation of non-linearity determining system 106 will now bedescribed for the case of determining vertical displacementnonlinearity. In process P1, probe 94 of measurement tool 90 is providedcoupled to positioning scanner 92. As shown in FIGS. 2-3, a sample 96 ispositioned on a fixture 98 that is capable of angling about a horizontalaxis 140. (Axis 140 could be a vertical axis to enable the X or Ynon-linearity determination.) Fixture 98 movement is controlled byfixture control 132, as will be described herein.

In process P2, scanner control 130 controls scanning of a surface 150 ofsample 96 at a first angle (α1) relative to probe 94 to attain a firstprofile, i.e., measured electronic representation of surface 150. Thatis, scanner control 130 controls the data recordation by measurementtool 90, positioning scanner 92, and any other required component ofmeasurement tool 90. As illustrated, first angle (α1) is substantially90° relative to the probe such that sample 96 is at or near horizontal;however, other angles may be used. (In the X or Y non-linearityassessment, the first angle is substantially parallel to either the X orthe Y axis while the second angle (as in process P3) is any anglesufficient to achieve the desired travel in the X or Y axis.) Sample 96may include, for example, a patterned integrated circuit (IC) chip.Preferably, sample 96 provides a smooth surface and the patternedsilicon provides a navigation aid to ensure the return of subsequentscanning to the same starting position to minimize sample surface 150variation due to stage positioning variance.

In process P3, scanner control 130 controls scanning surface 150 offirst sample 96 with the surface at a second angle (α2) relative toprobe 92 that is different than the first angle to attain a secondprofile. As illustrated, second angle (α2) is approximately 81° relativeto the probe; however, other angles may be used. That is, fixturecontrol 132 tilts sample 96 about horizontal axis 140 by approximately9°, e.g., by activating a motorized tilting mechanism in fixture 98. Inany event, second angle (α2) results in sample 96 being inclined,causing positioning scanner 92 to move probe 94 both laterally (X and/orY direction) and vertically (Z direction) to accommodate the inclinedsample 96.

In process P4, scanner control 130 repeats the scannings (process P2-P3)to attain a plurality of first profiles and a plurality of secondprofiles. It is understood that the repeating of scanning of sample 96does not necessarily have to occur with intermittent first angle andsecond angle positions, as shown in FIG. 2. If this intermittent processwas chosen, an alternative approach could be to use a single iterationof scans, do the fitting, the scan alignment of the residuals,subtraction, and then repeat this process to compare result 180(collection of scans) for evaluation. That is, as shown in FIG. 4,repetitive scanning at first angle could occur, followed by repetitivescanning at second angle. Any number of repetitive scans to ensureaccurate measurement may be used.

In process P5, determinator 134 determines a non-linearity ofpositioning scanner 92 using the different scanning angles to cancel outmeasurements corresponding to imperfections due to surface 150 of sample96. This process may take a variety of forms. In one embodiment, inprocess P5A, as shown in FIG. 4, averager 136 averages plurality offirst profiles 160 and averages plurality of second profiles 162,resulting in averaged first profiles 164 and averaged second profiles166. As shown in FIG. 5, in process P5B, best-line fitter 138 performs alinear regression (e.g., a Mandel or ordinary least squares regression)on averaged first profiles 164 and averaged second profiles 166 to fitthem to a first order best-fit line, and calculates residuals (shown indashed lines) from the first order best-fit lines. That is, the data isnormalized by the process of fitting the data to a straight line andcapturing the residuals. The residuals of the linear regression are thevertical deviations (both − and +) about the line. The residuals, bydefinition, have the slope of the line (and tilt of the sample) removed.Therefore, the residuals are the deviations from perfect linearbehavior. This “normalization” allows comparison of the flat state ofthe sample with next to no Z displacement with that of tilted state withlots of Z displacement. As also shown in FIG. 5, in process P5C, aligner140 aligns residuals of a best-fit line 170 of averaged first profiles164 and residuals of a best fit-line 172 of averaged second profiles166. The vertical dashed lines over residuals of best-fit line 170 ofaveraged first profiles 164 and residuals of best-fit line 172 ofaveraged second profiles 166 illustrate a potential non-linearity, whichcan be used for the alignment of residuals 172 to residuals 170. FIG. 6shows the result of process P5D in which differencer 142 subtracts theresiduals of averaged first profiles 164 from the residuals of averagedsecond profiles 166 after the aligner 140 positions residuals 170 and172 relative to each other. A result 180 identifies non-linearities ofpositioning scanner 92 since subtracting cancels out measurementscorresponding to imperfections due to surface 150 of sample 96. Thisprinciple is due to the invariance of surface 150 at the two differenttilt angles shown in FIGS. 3A and 3B. The tilt of sample surface 150 atsecond angle (α2) exercises the vertical Z displacement of positioningscanner 92 thus the subtraction of sample surface 150 variations leavesthe remaining Z displacement non-linearity. In process P5E, evaluator144 evaluates a result 180 (FIG. 6) of the subtracting to identify thenon-linearity of the positioning scanner, e.g., the areas that are notzero represent non-linearities in positioning scanner 92 operation.

In the example illustrated, the behavior shown in profiles 162 of FIG. 4indicates the non-linearity may be systematic. The Root-Mean-Square(RMS) of result 180 will result in a good estimate of the standarddeviation multiple (e.g., 3-sigma) uncertainty of the scanner due tonon-linearity. If uncertainty is too large, then a higher orderregression can remove this systematic non-linearity. This regressionequation would be used to correct for this systematic non-linearity ofthe scanner, and a new RMS would be calculated smaller than thepreviously calculated RMS yielding a smaller non-linear uncertainty.Returning to FIG. 2 in conjunction with FIG. 7, in an optionalembodiment, scanner control 130 may further be used to measure acalibrated Z height measurement sample 190, i.e., a calibrated sampleincluding a minimum of one known Z height standard, thus linking all ofthe Z values. A single calibrated step height standard is needed if thesurfaces of sample 190 have the similar roughness thus similar scanningprobe 94 to sample 150 interaction for the substrate and step surfacesof 190 in FIG. 7. If these probe to sample interactions aresignificantly different, a minimum of 2 calibrated standards would berequired to test that the scaling of the scanner is significantlydifferent from unity. Based on this measurement, calibrator 150 (FIG. 1)may calibrate an entire Z range of measurement tool 90 based on the Zheight measurement sample. Once the non-linearity 180 of the verticaldisplacement is determined, this information with a single standardfully describes the deviation from perfect linear behavior of the Zdisplacement for the tested range of the Z displacement. Similarly, forthe cases of the assessment of the X and Y linearity, a single pitchstandard would be required to calibrate the entire assessed X and Yscanner range.

As discussed herein, various systems and components are described as“obtaining” data (e.g., measurements, etc.). It is understood that thecorresponding data can be obtained using any solution. For example, thecorresponding system/component can generate and/or be used to generatethe data, retrieve the data from one or more data stores (e.g., adatabase), receive the data from another system/component, and/or thelike. When the data is not generated by the particular system/component,it is understood that another system/component can be implemented apartfrom the system/component shown, which generates the data and providesit to the system/component and/or stores the data for access by thesystem/component.

While shown and described herein as a method and system for determiningnon-linearity of positioning scanner 92, it is understood that thedisclosure further provides various alternative embodiments. That is,the disclosure can take the form of an entirely hardware embodiment, anentirely software embodiment or an embodiment containing both hardwareand software elements. In a preferred embodiment, the disclosure isimplemented in software, which includes but is not limited to firmware,resident software, microcode, etc. In one embodiment, the disclosure cantake the form of a computer program product accessible from acomputer-usable or computer-readable medium providing program code foruse by or in connection with a computer or any instruction executionsystem, which when executed, enables a computer infrastructure todetermine the non-linearity of positioning scanner 92. For the purposesof this description, a computer-usable or computer readable medium canbe any apparatus that can contain, store, communicate, propagate, ortransport the program for use by or in connection with the instructionexecution system, apparatus, or device. The medium can be an electronic,magnetic, optical, electromagnetic, infrared, or semiconductor system(or apparatus or device) or a propagation medium. Examples of acomputer-readable medium include a semiconductor or solid state memory,such as memory 122, magnetic tape, a removable computer diskette, arandom access memory (RAM), a read-only memory (ROM), a tape, a rigidmagnetic disk and an optical disk. Current examples of optical disksinclude compact disk-read only memory (CD-ROM), compact disk-read/write(CD-R/W) and DVD.

A data processing system suitable for storing and/or executing programcode will include at least one processing unit 114 coupled directly orindirectly to memory elements through a system bus 118. The memoryelements can include local memory, e.g., memory 112, employed duringactual execution of the program code, bulk storage (e.g., memory system122), and cache memories which provide temporary storage of at leastsome program code in order to reduce the number of times code must beretrieved from bulk storage during execution.

In another embodiment, the disclosure provides a method of generating asystem for determining non-linearity of positioning scanner 92. In thiscase, a computer infrastructure, such as computer infrastructure 102(FIG. 1), can be obtained (e.g., created, maintained, having madeavailable to, etc.) and one or more systems for performing the processdescribed herein can be obtained (e.g., created, purchased, used,modified, etc.) and deployed to the computer infrastructure. To thisextent, the deployment of each system can comprise one or more of: (1)installing program code on a computing device, such as computing device104 (FIG. 1), from a computer-readable medium; (2) adding one or morecomputing devices to the computer infrastructure; and (3) incorporatingand/or modifying one or more existing systems of the computerinfrastructure, to enable the computer infrastructure to perform theprocess steps of the disclosure.

As used herein, it is understood that the terms “program code” and“computer program code” are synonymous and mean any expression, in anylanguage, code or notation, of a set of instructions that cause acomputing device having an information processing capability to performa particular function either directly or after any combination of thefollowing: (a) conversion to another language, code or notation; (b)reproduction in a different material form; and/or (c) decompression. Tothis extent, program code can be embodied as one or more types ofprogram products, such as an application/software program, componentsoftware/a library of functions, an operating system, a basic I/Osystem/driver for a particular computing and/or I/O device, and thelike.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the disclosure.As used herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below are intended toinclude any structure, material, or act for performing the function incombination with other claimed elements as specifically claimed. Thedescription of the present disclosure has been presented for purposes ofillustration and description, but is not intended to be exhaustive orlimited to the disclosure in the form disclosed. Many modifications andvariations will be apparent to those of ordinary skill in the artwithout departing from the scope and spirit of the disclosure. Theembodiment was chosen and described in order to best explain theprinciples of the disclosure and the practical application, and toenable others of ordinary skill in the art to understand the disclosurefor various embodiments with various modifications as are suited to theparticular use contemplated.

What is claimed is:
 1. A system comprising: a measurement tool includinga probe coupled to a positioning scanner; a fixture for holding a samplefor scanning a surface of the sample with the surface at a first anglerelative to the probe to attain a plurality of first profiles, whereinthe first angle is substantially 90° relative to the probe, and scanningthe surface of the sample with the surface at a second angle relative tothe probe that is different than the first angle to attain a pluralityof second profiles, the second angle being able to be any angle thatresults in a predetermined amount of lateral travel of the probe; and adeterminator for determining a non-linearity of the positioning scannerusing the different scanning angles to cancel out measurementscorresponding to imperfections due to the surface of the sample.
 2. Thesystem of claim 1, wherein the probe is a non-contacting probe.
 3. Thesystem of claim 1, wherein the sample includes a patterned integratedcircuit (IC) chip.
 4. The system of claim 1, wherein the second angle isapproximately 81° relative to the surface of the sample.
 5. The systemof claim 1, further comprising: a calibrator for calibrating an entire Zrange of the measurement tool based on a Z height measurement sample. 6.The system of claim 1, wherein the measurement tool includes a scanningprobe microscope (SPM).
 7. The system of claim 1, wherein thedeterminator: averages the plurality of first profiles and averages theplurality of second profiles; fits the averaged first profiles and theaveraged second profiles to a first order best-fit line; aligns theaveraged first profiles and the averaged second profiles; subtracts thebest-fit line of averaged first profiles from the best-fit line ofaveraged second profiles; and evaluates a result of the subtracting toidentify the non-linearity of the position scanner.
 8. A scanning probemicroscope comprising: a probe coupled to a positioning scanner; afixture for holding a sample for scanning a surface of the sample withthe surface at a first angle relative to the probe to attain a pluralityof first profiles, wherein the first angle is substantially 90° relativeto the probe, and scanning the surface of the sample with the surface ata second angle relative to the probe that is different than the firstangle to attain a plurality of second profiles, the second angle beingable to be any angle that results in a predetermined amount of lateraltravel of the probe; and a determinator for determining a non-linearityof the positioning scanner using the different scanning angles to cancelout measurements corresponding to imperfections due to the surface ofthe sample.
 9. The scanning probe microscope of claim 8, wherein theprobe is a non-contacting probe.
 10. The scanning probe microscope ofclaim 8, wherein the sample includes a patterned integrated circuit (IC)chip.
 11. The scanning probe microscope of claim 8, wherein the secondangle is approximately 81° relative to the probe.